The present invention relates to an articulated stand used in particular for the support of a measuring gauge. But it can also be used for any other purposes wherever an object needs to be fixed at a definite place in a definite position. Different articulated stands are already known for these purposes. They essentially consist of two articulated arms which are pivotable with respect to each other via a center joint and can be arrested in any position. The articulated arms have ball joints on their ends, the balls of which are provided with a bolt which is freely rotatable and pivotable within the degree of freedom defined by the ball joint. One of the bolts is fixedly mounted, for example, on a foot, while the other holds the item to be supported. Furthermore, the articulated stand has means for fixedly clamping the central pivot joint between the two articulated arms as well as the ball joints. There are particular clamping means which can be operated by means of a single handle, so that all the joints of the stand can be simultaneously clamped. Such articulated stands are generally employed for fixedly maintaining any items, for example for fixing parts which are intended to be soldered, glued or welded. Because of the easy release of the clamping mechanism, all joints can be moved with the same force, which is helpful for adapting a desired position of the item. But in connection with measuring gauge stations it is desired that the joints be clamped in a set sequence, which is attained by means of a particular layout of the clamping means. Mostly the known clamping means include elements with inclined bearing surfaces seated axially displaceable on the pivot axis of the two articulated arms, which can be moved in relation to each other by means of a threaded connection with at least one of these elements, which is provided with a conical surface, by use of a handle disposed on the pivot bolt. The conical oblique surfaces or bearing surfaces then act directly or indirectly on pushrods, seated longitudinally displaceable in the articulated arms, which finally clamp the balls in the ball joints with the latter.
Additionally, when pulling the handle tight, the two articulated arms are pressed against each other and clamped against each other. In a known articulated stand of this type a similar effect is attained with conical elements by means of clamping sleeves into each of which a groove extending vertically to the sleeve axis has been milled. As it were, this groove acts as a cone by serving as an abutment for a toggle lever which adjoins the pushrod with its other end. If the clamping sleeves are moved in relation to each other, the toggle levers are slightly pivoted in the abutments and therefore press on the pushrod ends. The longer the toggle levers are in this case, the greater the transfer of force and the lesser the attainable displacement path of the pushrods. In another known articulated stand, balls are used instead of toggle levers, in which case the conical elements are clamping sleeves with inclined bearing surfaces formed by conically milled grooves having a spherical cross section.
It is of course the goal of all these articulated stand devices to attain the greatest amount possible of precision and clamping force with as simple as possible a structure. The articulated stand is meant to be sturdily designed and constructed so that it can absorb as high as possible forces occurring at the ends of the articulated arms without a change of the position of the latter. So that the articulated stand, which is clamped via a single handle, is user-friendly particularly when used as a measuring gauge stand, clamping of the individual joints of such a measuring gauge stand should not take place at exactly the same time, as already mentioned. If this were the case, the clamped articulated stand would suddenly collapse upon itself when the restraint is removed. Instead, it would be helpful if, in the course of installing and clamping the measuring gauge, first the ball joint serving as the foot of the articulated stand would be clamped, then the central pivot joint and finally the ball joint which supports the measuring gauge by means of a measuring gauge support or a precise adjustment device. If the articulated stand operates in this manner, the degrees of freedom of the movement of the measuring instrument to be supported are limited step by step and additional stabilization to a certain degree is already assured. In this way it is possible to proceed step by step from rough positioning to exact setting of the position of the measuring instrument. This successive clamping of the individual joints is attained in customary devices by interposing pressure springs of different strengths between the individual transfer elements of the restraint.
The customary articulated stands are put together from a considerable number of individual parts. This makes their manufacture expensive and, if these individual parts are movable, they each cause a certain amount of variation by their movement. Every place where two movable parts abut, a transition point is created, where corresponding play is possible. But in the long run, every possible play increases the variation and results in correspondingly unstable measuring conditions at the supported measuring instrument.